Now that I'm home...the GK effects loop wants a line level signal, but your Boss only does instrument level. Don't bother with using the effects loop, just use it out front (straight into the amps input). You can try it to see if you prefer it very easily. In your reading, have you familiarized yourself with what an effects loop actually does? Have you read up on the order of effects?
Originally Posted by The Stoke
I've heard you can damage the smaller cab running both the 410 and 210 off one amp. Hence the two amps (one for each cab).
If both cabs are 8 ohms, that's true. Each cab is getting roughly half of the amps power. The 4X10 is dividing that power by 4, while the 2X10 is only able to divide it by 2. The 2X10 speakers are getting more power than everything else.
With that said, the 1001 RB-II is more than capable of blowing any cab if you turn it up loud enough. I'd have no problem running both cabs with it and leaving the BL600 at home. Just listen for signs of distress. If you sound like you're doing something bad, you probably are.
I can also eq each cab differently to get what I consider optimal tone from each cab. Can't help but shake the feeling I'm over thinking my rig.
That's all personal preference. If you like the sound you get from both rigs and can't get it from only using one amp, there is your answer. Having 3 separate signals sent FOH is a bit much IMO. No soundguy around here would deal with that unless my band hired them or we ran our own sound.
You can always try running less and see how it works out for you. I'd try the 1001 RB-II, MB-50E, and the 4X10...